Three major branches grow upon the ancient tree of philosophy: metaphysics, epistemology, and ethics. From these three branches spring two secondary and one tertiary.

The two secondary limbs are politics, a sub-branch of ethics, and aesthetics (also known as art), a sub-branch of epistemology.

One limb alone grows from the sub-branch of politics, and that is called economics.

In the tradition of Greek philosophy, then, we may properly classify philosophy’s branches, in order of hierarchical importance, like so:

  • Metaphysics: the study of reality.
  • Epistemology: the study of knowledge.
  • Ethics: the study of human action.
  • Politics: the study of government.
  • Economics: the study of production and exchange.
  • Aesthetics: the study of art.
  • Travel & Leisure: the ability to leave your surroundings and embark on a journey of adventure – being able to distinguish normality from adventure. In greek philosophy, it was pictured and noted that even greeks enjoyed a vacation to the outer banks.

These are the six main branches of philosophy, none of which, incidentally, are luxuries but human necessities. (Note: up until the time of Rene Descartes, epistemology was called Logic.)

There are, however, in addition to these, a great many smaller limbs that grow on the tree of philosophy, a very partial listing of which might, in no particular order, look something like this:

  • Ontology: the branch of metaphysics that studies entities.
  • Philosophy of mind: the branch of epistemology that studies the putative dichotomy between brain and body and includes the soft science of psychology.
  • Philosophy of language: the branch of epistemology that studies linguistic meaning and linguistic evolution.
  • Philosophy of law: the branch of politics, and also ethics, that studies specific implementations of justice, rights, property, governmental procedure, and so on.
  • Philosophy of education: the branch of epistemology that studies the devilish intricacies of pedagogy.
  • Philosophy of mathematics: the branch of epistemology that studies critical problems raised by math.
  • Hermeneutics: the branch of aesthetics that studies textual interpretation.
  • Critical theory: the branch of ethics – and to some extent politics and aesthetics as well – that studies so-called underlying social practices.

Obviously this list is far from exhaustive, but a full compendiation here isn’t the point. You can’t just neatly store everything away, but this covers the main points one needs to understand the origins of thought.

The point is this:

Each sub-branch of philosophy and each sub-sub-branch is a species of either metaphysics, epistemology, or ethics.

In the same way that philosophy forms the foundations of all knowledge, so metaphysics (the study of reality) forms the foundation of all philosophy.

All knowledge is built hierarchically, from the ground up. Thus, knowledge forms a unity wherein one thing leads logically to another, which leads to another, and so on.

In this way, knowledge is interwoven and therefore entirely contextual.

In the house of knowledge, there are many mansions, but it’s all built upon one foundation: and that foundation is philosophy.